How Much Sunlight Do Outdoor Cannabis Plants Need?

Just like any other plant, cannabis needs light to grow. Indeed, if you want to fill your bags with an abundance of fat buds come harvest, cannabis will need a whole lot of light—much more so than most other plants. The power of the sun encourages robust growth, allowing your plants to mature buds of peak potency and flavour.

But how much sunlight do cannabis plants really need? Is there such a thing as too much? And, what can you do if they don’t get enough? Let’s take a closer look!

WHY SUNLIGHT IS IMPORTANT FOR GROWING CANNABIS

Along with choosing good genetics, a suitable substrate, and the right nutrients, no consideration is as important for growing healthy cannabis plants as lighting. This is why indoor growers drop good money on powerful lights; without them, cannabis plants can’t really thrive.

The science behind this phenomenon is that light provides plants with energy needed for photosynthesis. Or, less scientifically spoken, more light means bigger, healthier plants and fatter buds!

Aside from photosynthesis, light plays another vital function. Photoperiod cannabis plants move through their vegetative and flowering phases based on the hours of light they receive. When the daylight hours naturally decrease in late summer and fall, this signals the plant to start flowering.

HOW MUCH SUNLIGHT DO CANNABIS PLANTS NEED?

Unless heat waves are an issue, you should aim to plant your cannabis where it can access as much sunlight as possible. If you want a little more control over their location, consider planting in large containers that you can move around based on conditions. That way, you can always relocate your plants to a spot with dappled or partial sunlight if need be.

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Before you commit to planting in a particular spot, make sure the location gets at least 5 hours of direct sunlight, along with several hours of indirect sun. If the spot gets less than that, your harvest will likely turn out poor at best. Remember: more sun equals fatter buds!

FOR AUTOFLOWERING PLANTS

Autoflowering cannabis plants flower under nearly any conditions, which makes them ideal for beginners. But, this doesn’t mean they don’t need light! Just like with feminized photoperiod plants, you’ll want to ensure they can get as much light as possible for healthy growth and optimal harvests. Given that autoflowers tend to produce less weed than their photoperiod counterparts, maximising sun exposure can really help bridge the gap in yield.

Most autoflowers veg for about 3–4 weeks before automatically moving into flower. Because their lifespan is also much shorter than feminized photoperiod plants, they can provide multiple crops in a single growing season if you plan wisely.

If you’re planting autoflowers outdoors, it’s best to start them at the beginning of summer when daylight hours and sun intensity are already aplenty. Most autoflowers will be ready in just 60–70 days from germination, so they’ll race right on through to harvest. Grown several weeks apart, you can harvest cannabis until autumn!

FOR FEMINIZED (PHOTOPERIOD) PLANTS

Compared to autoflowers, feminized photoperiod cannabis stays in the vegetative stage as long as it receives 15+ hours of sunlight per day. When planting feminized cannabis outdoors in spring, it will spend a few solid months in the vegetative phase. When the daylight hours decrease at the time of the summer solstice, it will start to flower.

The exact duration feminized cannabis will need for flowering depends on the strain. Some may grow and flower faster, ready to harvest at the end of summer. Other strains, like long-blooming sativas, will take much longer, ready to harvest around November.

So, when growing feminized cannabis outdoors, sufficient light not only ensures robust growth and great yield potential, but also that plants can move from veg to flower successfully. Because of this, planting your feminized cannabis at the right time is arguably more crucial than with autoflowers. You want to maximise the season to support optimal growth while allowing your plants sufficient time to flower before the fall frost and rains arrive.

WHAT IF THERE IS TOO MUCH SUNLIGHT?

If you’re growing cannabis outdoors in a northern climate, like in the UK, the Netherlands, Poland, or Germany, the intensity of the sun likely won’t be an issue for your cannabis plants. But, if you happen to be further south, like in the Meditteranean, the sun can be quite intense, and this can become a problem in itself. Rather than worrying about your plants not getting enough sun, you will actually need to look into sun protection.

You have a couple of suitable options here. First, if you’re planting directly in the ground, look around for a spot where your plants get plenty of sun in the morning, then shade for much of the afternoon. If your weed is protected by a shed or some trees, it may prevent them from being stressed by excess heat/light. Don’t plant your weed facing south where the hot noon sun will burn it, but instead choose a spot that faces east or west so there is some shade during the hottest time of the day.

You can also look into erecting sun-shading equipment around your plants if need be. The other option, as mentioned above, is to circumvent this issue by planting your cannabis in containers that can be moved around depending on conditions. While you’ll still need to find a suitable spot for them to grow, if temperatures get really high during peak summer, you can relocate your plants to somewhere less intense.

WHAT IF THERE ISN'T ENOUGH SUNLIGHT?

Unfortunately, it’s much harder to add light outside than it is to “subtract” it. This is why it’s crucial to pick a spot where your plants can bask in as much sun as possible. Take advantage of large pots to move your cannabis around so it gets the entire day’s sunlight.

Alternatively, if you have the resources to hand, and sunlight exposure is really flagging, consider using supplemental artificial lighting to boost your plant’s productivity. By giving your plants additional hours of light at the beginning/end of their day indoors, you may be able to boost development and productivity. Just make sure to give them the right amount of light for their phase of growth, as you don’t want to revert a blooming plant back to veg.

Steven Voser

Steven Voser is an independent cannabis journalist with over 6 years of experience writing about all things weed; how to grow it, how best to enjoy it, and the booming industry and murky legal landscape surrounding it.

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